State of the Climate 2012 provides an updated summary of long-term climate trends. It notes that the long-term warming trend has not changed, with each decade having been warmer than the previous decade since the 1950s. The warming trends observed around Australia are consistent with global-scale warming that has been measured during recent decades, despite 2010 and 2011 being the coolest years recorded in Australia since 2001. Global-average surface temperatures were the warmest on record in 2010 (slightly higher than 2005 and 1998). 2011 was the world’s 11th warmest year and the warmest year on record during a La Niña event. The world’s 13th warmest years on record have all occurred in the past 15 years.

There has been a general trend towards increased spring and summer monsoonal rainfall across Australia’s north during recent decades, and decreased late autumn and winter rainfall across southern Australia. The summary shows that the very strong La Niña event in 2010 followed by another in 2011 brought the highest two-year Australian-average rainfall total on record.

State of the Climate 2012 also highlights the increase in global sea level and notes sea-level rise around Australia since 1993 is greater than, or equal to, the global average. Our observations show that sea-surface temperatures around Australia have increased faster than the global average. The concentrations of long-lived greenhouse gases in the atmosphere reached a new high in 2011. Annual growth in global fossil-fuel CO2 emissions between 2009 and 2010 was 5.9 per cent, reversing a small decline of 1.2 per cent recorded between 2008 and 2009 during the global financial crisis.

Fossil-fuel CO2 emissions increased by more than three per cent per year from 2000 to 2010.

The concentration of CO2 in the atmosphere in 2011 was 390 parts per million – higher than at any time for the past 800,000 years.

The main cause of the observed increase in CO2 concentration in the atmosphere is the combustion of fossil fuels since the industrial revolution.

Then there are some graphs:

NASA, the US National Climatic Data Centre, and the UK Hadley Centre have each produced global temperature datasets. The graph shows the annual means calculated from the three datasets. Years beginning with an El Niño (orange) and La Niña (blue) are shown after suitable data became available in 1950 (note: 2010 began with an El Niño, and a La Niña then started mid-year).

[I find the last comment in parenthesis startling, no doubt reflecting my lack of understanding of ENSO]

1000-year records of southern hemisphere background concentrations of CO2 parts per million (ppm – orange), N2O parts per billion (ppb – blue) and CH4 (ppb – green) measured at Cape Grim Tasmania and in air extracted from Antarctic ice and nearsurface levels of ice known as firn.

Fossil-fuel CO2 emissions (orange) increased from 2000 to 2010 at more than 3 per cent per year. The growth from 2009-2010 was 5.9 per cent, reversing a small decline of 1.2 per cent the previous year related to the global financial crisis. Observations of total CO2 emissions (from fossil fuel burning and land-use change – grey) are tracking along the higher end of expected emissions.

High-quality global sea-level measurements have been available from satellite altimetry since the start of 1993 (red line), in addition to the longer-term records from tide gauges (blue line, with shading providing an indication of the accuracy of the estimate). Sea level rose at a global-averaged rate of about 3 mm per year between 1993 and 2011, and 1.7 mm per year during the 20th century as a whole.

Changes in average temperature for Australia for each year (orange line) and each decade (grey boxes), and 11-year average (black line – an 11-year period is the standard used by the Intergovernmental Panel on Climate Change). Anomalies are the departure from the 1961-1990 average climatological period. The average value for the most recent 10-year period (2002–2011) is shown in darker grey.

Contrary to what the self-named climate sceptics propose, Naomi Oreskes the bias of scientists is not toward “alarmism” but that they have been overly cautious: